Network equipment system providing surge protection and DC blocking bypass functionalities

ABSTRACT

A network equipment system comprises a communication apparatus, an equipment protector block connected between the communication apparatus and a subscriber premise DSL network termination device (NTD), and a protection module mounted on the equipment protector block. The protection module includes circuitry configured for providing surge protection functionality, for providing AC coupling-DC blocking functionality, for providing DC blocking bypass functionality, and for enabling said DC blocking bypass functionality to be selectively activated and deactivated. The protection module facilitates such functionality in association with the communication apparatus and the subscriber premise DSL NTD.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of co-pending U.S. patentapplication Ser. No. 10/404,231 filed Apr. 1, 2003 entitled “ACCOUPLING-DC BLOCKING SURGE PROTECTION MODULE WITH DC BLOCKING BYPASSFUNCTIONALITY”, and having a common applicant herewith.

FIELD OF THE DISCLOSURE

The disclosures herein relate generally to surge protection devices andmore particularly to surge protection devices configured for providingDC blocking functionality and/or AC coupling functionality.

BACKGROUND

Local exchange carrier access network equipment, such as Digital LoopCarriers (DLCs) and Digital Subscriber Access Multiplexers (DSLAMs),provide Digital Subscriber Line (DSL) service to subscribers overtwisted wire pairs or “loops”. The electronic components and systemscomprised by DLC's and DSLAM's are protected through the use ofprotection devices (surge protectors) located near the network equipmentfrom damage by induced voltage surges (e.g., via lightning strikes)picked up by the twisted wire pairs. Such surge protectors areessentially transparent to the network services (Plain Old TelephoneService (POTS), Asymmetrical Digital Subscriber Line (ADSL), etc.) whilethey shunt momentary high voltage surges to ground. The protectors arealso essentially transparent to metallic loop test systems that test forfaults on the twisted wire pair between subscriber premise equipment andupstream network equipment.

When remote electronics, typically located on the outside of asubscriber's premise, are powered over the twisted wire pair from anetwork equipment site or another remote location, power feed equipmentfor providing power to such remote electronics is coupled to the twistedwire pair. When the network electronics are AC coupled to the twistedwire pair, the power feed equipment can be directly bridged to thetwisted wire pair. However, when the network electronics are DC coupledto the twisted wire pair, as would typically be the case for acombination POTS/ADSL line card, simple direct bridging cannot beimplemented. For example, the voltage provided by the power feedequipment (e.g., nominally −200Vdc) conflicts with the POTS “talkbattery” voltage (nominally −48Vdc).

Conventional approaches to providing a DC voltage on a twisted wire pairfrom power feed equipment are known. In cases where POTS is notrequired, conventional combination POTS/ADSL cards are replaced byADSL-only cards, thus allowing the power feed to be applied without anyconflicts. In cases where POTS and ADSL functionality is facilitated,even though the POTS signal is unused, combination POTS/ADSL signals arepassed through a high pass filter for eliminating unused POTS talkbattery voltage, thereby allowing resulting filtered signals to bebridged with the power feed.

However, such conventional approaches for providing the DC power feedover the twisted wire pair have significant limitations associatedtherewith. In the case where conventional combination POTS/ADSL cardsare replaced by ADSL-only cards, such a conventional approach would havean adverse expense associated with replacing POTS/ADSL combination cardsthat are already deployed in a network with newly developed ADSL-onlycards. Furthermore, replacing conventional combination POTS/ADSL cardswith ADSL-only cards would require rewiring in the DLC or DSLAM cabinetsor require installation of cross-connect cabinets for connectingreassigned lines out of the DLC or DSLAM cabinets. In the case where acombined POTS/ADSL signal is filtered, such high pass filtering of asignal from a DLC or DSLAM will prevent complete metallic loop testing(MLT), as MLT uses the spectrum down to DC for many tests (e.g.,detecting resistive faults, detecting presence of foreign voltages,etc). Additionally, it is hard to selectively gain access to anindividual twisted wire pair because multi-pair cable harnesses andmulti-pair connectors are often pre-wired with the equipment incabinets, leaving little available space to accommodate access toadditional pairs and for the high pass filtering equipment.

Accordingly, a solution for enabling the combination of surgeprotection, DSL signal transmission, full metallic loop testing andbridging of a DC power feed to be facilitated in association with atwisted wire pair in a manner that overcomes limitations associated withconventional solutions would be useful.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a network equipment protection module in accordance withan embodiment of the disclosures made herein.

FIG. 2 depicts an embodiment of a network equipment system in accordancewith an embodiment of the disclosures made herein.

DETAILED DESCRIPTION OF THE DRAWINGS

Embodiments of the disclosures made herein relate to a network equipmentprotection module for use with central office or remote DSL networkequipment (e.g., DSLAMs, DLCs, etc). Such a network equipment protectionmodule enables the combination of surge protection, DSL signaltransmission, full metallic loop testing (MLT) and bridging of a DCpower feed to be facilitated in association with a twisted pairtransmission line (also referred to herein as a twisted wire pair) in amanner that overcomes limitations associated with conventional solutionsfor providing such functionality. Accordingly, voltage provided by powerfeed equipment (e.g., nominally 200Vdc) may be provided to a subscriberpremise DSL network termination device (NTD) over the twisted pairtransmission line, without inhibiting full MLT functionality. A DSL NTDis an example of such a subscriber premise DSL NTD that relies onvoltage provided by power feed equipment via an attached twisted pairtransmission line. A DSL NTD is an active device powered from upstreampower feed equipment and which, in at least one embodiment, providesPOTS functionality via ADSL data transmission (i.e., POTS talk batteryvoltage not provided over an attached twisted pair transmission line),

Network equipment protection modules in accordance with embodiments ofthe disclosures made herein (i.e., an AC coupling-DC blocking surgeprotection module with DC blocking bypass functionality) offer a numberof benefits. One benefit is that they are direct replacements forconventional surge protectors as used in conventional protector blocks.Accordingly, they do not require any re-wiring of the twisted pairtransmission lines at the DLC or DSLAM cabinet. Another benefit is thatthey don't require costly replacement of combination ADSL/POTS cards atthe DLC or DSLAM, thus being a less expensive approach. Still anotherbenefit is that the overall approach requires no additional space in aDLC or DSLAM. Yet another benefit is that they do not inhibit fullmetallic loop testing.

Turning now to discussion of specific drawings, a network equipmentprotection module 10 in accordance with an embodiment of the disclosuresmade herein is depicted in FIG. 1. The network equipment protectionmodule 10 includes surge protection circuitry 12 configured forproviding surge protection functionality, AC coupling-DC blockingcircuitry 14 configured for providing AC coupling-DC blockingfunctionality and DC blocking bypass circuitry 16 configured forproviding DC blocking bypass functionality. In at least one embodimentof the disclosures made herein, the surge protection circuitry 12, theAC coupling-DC blocking circuitry 14 and the DC blocking bypasscircuitry 16 are all contained in a discrete packaging device 19.

An enclosure having a plurality of contacts mounted thereon andexternally accessible therefrom is an example of the discrete packagingdevice 19. In accordance with an embodiment of the disclosures madeherein, the discrete packaging device 19 is configured for being mountedon an unmodified commercially-available equipment protector block, whichis OEM-configured for having conventional surge protectors mountedthereon. One example of such a commercially available equipmentprotector block is a 310-series equipment protector block offered byAVAYA Incorporated. One example of such conventional surge protectors isa 5-pin surge protector module offered by Marconi CommunicationsIncorporated

The AC coupling-DC blocking circuitry 14 includes a first capacitor 18and a second capacitor 20 connected in series with a first power lead 22and a second power lead 24, respectively (i.e., a pair of power leads).The first capacitor 18 and the second capacitor 20 represent oneembodiment of means for providing AC coupling-DC blocking functionality.In at least one embodiment of the AC coupling-DC blocking circuitry, thefirst capacitor 18 and the second capacitor 20 have a capacitance ofabout 1 micro Farad. It will be appreciated that the specificcapacitance for the capacitors (18, 20) will be specified dependent uponthe specific implementation of the network equipment protection module10.

The DC blocking bypass circuitry 16 includes a control portion 26connected between first power lead 22 and the second power lead 24. Thecontrol portion 26 is configured for enabling a first shunt 28 and asecond shunt 30 to be selectively connected and disconnected across thefirst capacitor 18 and the second capacitor 20, respectively. When asuitable DC voltage is applied across the pair of power leads (22, 24),the control portion 26 of the DC blocking bypass circuitry 16 isactivated (i.e., in response to current flows through the controlportion 26) and acts to disconnect the shunts (28, 30) from across therespective one of the capacitors (18, 20) whereby DC blockingfunctionality is activated. When the DC voltage is removed from acrossthe pair of power leads (22, 24), the control portion 26 of the DCblocking bypass circuitry 16 is de-activated, thereby deactivating(i.e., bypassing) DC blocking functionality by allowing the shunts (28,30) to be connected across the respective one of the capacitors (18,20). In this manner, the DC blocking bypass circuitry 16 is configuredfor enabling the DC blocking bypass functionality to be selectivelyactivated and deactivated. The DC blocking bypass circuitry 16represents one embodiment of means for providing DC blocking bypassfunctionality.

A pair of normally-closed relay paths is an example of the first shunt28 and the second shunt 30. It is contemplated herein that such a pairof normally-closed relay paths may be facilitated via a single relay ora plurality of relays (e.g., 2 relays). An actuation coil relay of asingle relay is one example of the control portion 26 of the DC blockingbypass circuitry 16. Actuation coils of a pair of relays having aresistor connected therebetween (i.e., for limiting current flow throughthe actuation coils) are another example of the control portion 26 ofthe DC blocking bypass circuitry 16. Embodiments of the disclosures madeherein are not limited to solid-state and mechanical relays, but mayutilize any useful circuitry or component that provides relayfunctionality.

The surge protection circuitry 12 is connected between the pair of powerleads (22, 24) and a ground lead 32. A Transient Voltage Suppression(TVS) device such as a SIDACtor brand TVS device or similar TVS deviceis an example of the surge protection circuitry 12. The surge protectioncircuitry 12 is an example of means for providing surge protection.

FIG. 2 depicts an embodiment of a network equipment system 100 inaccordance with an embodiment of the disclosures made herein. Thenetwork equipment system 100 includes a communication apparatus 102, anequipment protector block 104 and a plurality of network equipmentprotection modules 10 (as disclosed above in reference to FIG. 1)mounted on the equipment protector block 104. The equipment protectorblock 104 is connected between the communication apparatus 102 and asubscriber premise DSL NTD (not shown) via a twisted pair transmissionline 105. In practice, the equipment protector block in a DLC and DSLAMis pre-installed and pre-wired to the communication apparatus 102 (or atleast to a backplane through which connections to such apparatus ismade).

A DC voltage (e.g. −200Vdc), which is supplied by power feed equipment(not shown), is bridged onto the twisted pair transmission line 105(e.g., at a junction block). Such power feed equipment may be locatedlocally or remotely with respect to the communication apparatus 102. TheDC blocking circuitry 16 of the network equipment protection modules 10inhibits the DC power feed voltage from being applied to thecommunication apparatus 102.

The communication apparatus 102 includes DSL multiplexing equipment 106and test equipment 108. The equipment protection block 104 is connectedto the DSL multiplexing equipment 106 and/or the test equipment 108. Itis contemplated that the equipment protection block 104 is connecteddirectly to the DSL multiplexing equipment 106 and that the testequipment 108 transmits signals downstream through the equipmentprotection block 104 via the DSL multiplexing equipment 106.

A DLC (e.g., a common control shelf and channel bank assemblies) and aDSLAM are two examples of the DSL multiplexing equipment 106. In atleast one embodiment of the disclosures made herein, the test equipment108 is configured for performing Metallic Loop Test (MLT) functionality.Accordingly, MLT test equipment is an example of the test equipment 108.The combination of the equipment protector block 104 and at least one ofthe network equipment protection modules 10 is an example of a networkequipment protection apparatus.

In operation, a plurality of network equipment protection modules 10 isplugged into (or otherwise operably mounted on) the equipment protectionblock 104. One or more of the network equipment protection modules 10may replace one or more conventional surge protectors mounted thereon.Each one of the network equipment protection modules 10 is configuredfor providing surge protection, AC coupling-DC blocking functionalityand DC blocking bypass functionality. The DC blocking bypassfunctionality allows full metallic loop testing to be performed whilethe power feed (i.e., DC voltage) is removed from the twisted pairtransmission line 105. Use of the preinstalled and pre-wired equipmentprotection block 104 and the selective application of the equipmentprotection modules 10 allows power to be provided to individual twistedpair transmission lines without requiring line cards to be replaced, OSSreassignment, rewiring, and service outages to customers on the sameline cards who are retaining POTS capability.

In the preceding detailed description, reference has been made to theaccompanying drawings that form a part hereof, and in which are shown byway of illustration specific embodiments in which the invention may bepracticed. These embodiments, and certain variants thereof, have beendescribed in sufficient detail to enable those skilled in the art topractice the invention. It is to be understood that other suitableembodiments may be utilized and that logical, mechanical and electricalchanges may be made without departing from the spirit or scope of theinvention. To avoid unnecessary detail, the description omits certaininformation known to those skilled in the art. The preceding detaileddescription is, therefore, not intended to be limited to the specificforms set forth herein, but on the contrary, it is intended to coversuch alternatives, modifications, and equivalents, as can be reasonablyincluded within the spirit and scope of the appended claims.

1. A network equipment system, comprising: a communication apparatus; anequipment protector block connected between the communication apparatusand a subscriber premise DSL network termination device (NTD); and aprotection module mounted on the equipment protector block and includingcircuitry configured for providing surge protection functionality, forproviding AC coupling-DC blocking functionality, for providing DCblocking bypass functionality and for enabling said DC blocking bypassfunctionality to be selectively activated and deactivated; wherein theprotection module facilitates said functionality in association with thecommunication apparatus and the subscriber premise DSL NTD.
 2. Thenetwork equipment system of claim 1 wherein: the communication apparatusincludes DSL multiplexing equipment and test equipment; and theequipment protection block is connected to at least one of said DSLmultiplexing equipment and said test equipment.
 3. The network equipmentsystem of claim 2 wherein the DSL multiplexing equipment is one of aDigital Loop Carrier (DLC) and a Digital Subscriber Line AccessMultiplexor.
 4. The network equipment system of claim 3 wherein the testequipment is configured for performing Metallic Loop Test (MLT)functionality.
 5. The network equipment system of claim 13 wherein: saidcircuitry is contained in a discrete packaging device; the discretepackaging device is mounted on the equipment protector block; and theequipment protector block is an unmodified commercially-availableequipment protector block that is OEM-configured for having conventionalsurge protectors mounted thereon.